What ammunition does a Marlin 1887 shoot if it has 32W stamped under the hex barrel?
I'm assuming you have a Marlin model 1889, not 1887, as they never made a model 1887. The 1889 does have a patent date of 1887 on the barrel, so this is a common mistake. Any Marlin marked ".32W" on the barrel will normally be chambered for the .32-20 Win. cartridge.
What kind of ammunition do you need for a Remington 700sps 7mm mag?
The caliber of ammunition the rifle uses is usually roll-stamped on the right side of the barrel, just in front of the receiver. For example: if it says "7mm Remington (Rem.) magnum (mag.) you would need to buy that type of ammunition as sold by Remington, Federal or any of the other companies offering this type of ammo in whichever bullet weight you prefer to shoot.
Can you use 3030 bullets in a 410 shotgun?
No. You can only fire .410 shotgun shells in it. You should never attempt to fire a different ammunition than is stamped on the barrel, even if it appears to fit. If the pressure is too high, or the cartridge doesn't fit, at the best your gun will not shoot properly. At the worst it can explode and kill you.